Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H,W = map(int,input().split())

graph = [input() for i in range(H)]
q = deque([(0,0)])
dist = [[-1] * W for i in range(H)]
dist[0][0] = 1

while q:
    y, x = q.popleft()
    L = [(1,0), (-1,0), (0,1), (0,-1)]
    for i, j in L:
        if ((0 <= y+i <= H-1 and 0 <= x+j <= W-1)
            	and dist[y+i][x+j] == -1
            	and graph[y+i][x+j] == "."):
        	dist[y+i][x+j] = dist[y][x] + 1
        	q.append((y+i, x+j))

white = 0
for i in range(H):
    white += graph[i].count(".")
    
if dist[H-1][W-1] == -1:
    print("-1")
else:
    ans = white - dist[H-1][W-1]
    print(ans)